Telephone-exchange system.



E. B. CRAFT & l. N. REYNOLDS.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED 1u1Y23. 1915.

1,205,518. Patented Nov. 21, 1916.

3 SHEETS-SHEET I.

D //7ve/7f0/ s.' W/fnesses: Edward 5. C/aff.

M Jam. /v. Reyna/d E B. CRAFT & 1 N. REYNOLDS TELEPHONE EXCHANGE SYSTEM.

APmQATIQN mm 1uLv2s. m5.

1,205,518. Patented Nov. 21, 1916.

3 SHEETS-SHEET 3.

& f

2 Edward 5. Craft John N Reyna/d3.

W/fn asses.

UNITED STATES PATENT OFFICE.

GREENWICH, CONNECTICUT, ASSIGNORS, BY MESNE ASSIGNM'ENTS,-TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Nov. 21, 1916.

To all whom it may concern:

Be it known that we, EDWARD B. CRAFT and JOHN N. REYNOLDS, citizens of the United States, residing at Hackensack, in the county of Bergen and State of New Jersey, and at Greenwich, in the county of Fairfield and State of Connecticut, respectively, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates particularly to improvements in telephone systems of the type in which the calls are brought in to the operator through the medium of switches that operate, or are manipulated, to extend any one of the lines which may be calling to any one of a number of connecting circuits with which the operator may be provided.

It is the object of the invention to provide means in an organization of this character whereby the operator, to whom the circuit of a calling line is thus extended, may be informed of the identity of the calling line so that she may be guided in her treatment of the call. To this end there is associated with each of the lines means for impressing upon the line a characteristic electrical condition such as to distinguish each line from the other lines, and the operator is provided with a device, which she may bring into connection with the circuit over which a calling line is extended to her, to determine the identity of that line. The characteristic electrical condition which is preferably employed for the identification of the different lines is one which involves the impressing upon the various lines of groups of impulses, the impulses in the groups applied to each line preferably corresponding with the digits in the line number of the particular line. The means which is adapted to impress these impulses upon the various lines is normally inactive, and is made active by the operator when she wishes to ascertain the identity of the line which has been extended to her position.

One feature of the invention is the provision of a local conductor associated with each of the lines and its extension circuit to the operators position, which local @011 wh1ch thus serves as an identifying conductor. The identifying conductor and its assoc ated devices have to do, first, with that ldentlfication of the line which is concerned with its calllng condition, and which controls the extending of the line to the operator; and, second, with the identification that has to do with the ascertaining by the tppe'aislor of the number of the line thus exen e The invention will be explained more in detail byreference to the accompanyingdrawings, which represent one of the forms in which the invention may be embodied, and in which Figure 1 illustrates the calling subscribers lme, the hue finder and the associated controll ng apparatus; Fig. 2 illustrates the connecting cord finder with its associated clrcuits and controlling apparatus; and Fig. 3 illustrates the connecting cord circuit and the operators circuit-with their associated apparatus. V i

The system in connection with which this embodiment of the invention is illustrated,

elements are provided.

The calling subscribers station l'of Fig. 1 is provided with the usual switch hook 2 for closing the circuit of the line conductors 3 aud t. Whenthis circuit is closed on the initiation of a call, current flows from battery 5 through relay 6, which is common to a group of lines terminating on the contact points of a group of line finder switches, through one winding of line relay 7, contact 8 of cutofi relay 9, line conductor 4,-

switchhook 2, line conductor 3, contact 10 of cutoff relay 9, and the other winding of line relay 7 to earth. The current in this path actuates group relay 6 and line relay.

7. The actuation of relay 6 closes the contact 12 of that relay, thus completing a circuit from earth, through conductor 13, se-

quence switch contact 1021 and sequence switch operating magnet 100, to battery 5 and earth. p

Sequence switch 100 and sequence switches 200, 300 and 400 may be similar to that illustrated inthe patent to F. R. McBerty, No.

1,009,080 dated November 21, 19l1, or of any other suitable type.

Switch 100 controls sequence switch contacts 101 to 114, inclusive. Contact 101 of sequence switch 100 is arranged to close the local circuit for the sequence switch operating magnet in all positions of the switch except those indicated by the figures adJacent to-contact 101. This provides that the switch may stop only in the position indicated. The other sequence switch contacts 102 to 114, inclusive, are closed only in the positions indicated by the figures ad acent .to the respective contacts.

The current flowing through conductor 13, sequence switch contact 102-1 and the operating magnet of sequence switch 100, causes the movement of the sequence switch from its first to itsfourth position. As the sequence switch passes from its first to its fourth position, contact v1063% is closed, thus sending an impulse over conductor 41 to start the cord finder sequence switch 200 of Fig. 2, the operation of which will be hereinafter described.

In the fourth position of the sequence switch 100, circuit is completed from battery 5 through the brush operating magnet 43, sequence contact 1074 and back contact 34 of relay 29., to ground, Current in this path actuates the brush operating clutch magnet 43, causing the brush carriage shaft 44 to rotate in a counter-clockwise direction. As the shaft 44, rotates, the four brushes 40, 47, 48 and 49 drag over the contact points of the various line terminals in the path oftheir movement. When the brushes in their travel engage contact points/42, 50, 51 and 52 of the calling line, a circuit is completed from battery 5 through non-inductive resistance 55, contact 54 of the line relay 7 conductor 19, contact point 42 and brush 40, sequence switch contact 1044, conductor 26,-high resistance coil 27 of test 'relay 28, and the coil of test relay 29 to ground. The resistance of 55 is low as compared with the resistance of the clutch magnet 17 in the other and normally closed branch of the circuit. Consequently, current in this path actuates test relay 28,

thereby closing contact 30 and shunting the high resistance winding 27 by the low resistance winding 31. This reduces the test potential on contact 42 so that the subscribers line in question cannot be selected by another switch of the group 'in which it terminates. Relay 29 also operates, there- 1 thus stopping the rotation of the shaft 44 and. leaving the brushes 40, 47, 48 and 49 in engagement with the contact points 42, 50, 51and 52 of the calling line.

In order to prevent relay 29 from operating and thus stopping the rotation of brush shaft 44 before the brushes are in perfect contact with points 42, 50, 51 and 52, an intermittent shunt path is provided for this relay by way of sequence switch. contact 1034, contact arm 38, roller track brush 37 and track 24, to'ground. This path is open only when the roller of arm 37 falls into a depression in track 24, in which position the brushes 40, 47, 48 and 49 will be centered on their respective contact points.

The operation of test relay 29-closes contact 35, thus completing a circuit from ground, through conductor 36,. sequence switch contact 1084 and the coil of holding magnet 57 to battery. The function of the holding magnet 57 is to prevent the inertia of the clutch disk of the brush carriage from carrying the brushes beyond the desired position. Contact 35 of relay 29 also completes a circuit through conductor 36, sequence contact 1054 and the operating magnet of sequence switch 100 to battery 5, thus moving the sequence switch out of its fourth and into its fifth position. In this position a circuit is closed from ground through resistance 46, sequence switch contact 109-5, brush 47 contact 50 of the line finder and the coil of cut-off relay 9 to battery. This operates the cut-01f relay and opens the circuit of group relay 6 and line relay7; The potential of contact 50'is thus altered, this change in potential providing the busy test potential for the multiple contacts of the callin line which may extend either to multiple acks at a manual board or to terminals of automatic connector switches.

In the fifth position of sequence switch 100, the lever of contact 102, which has. been standing in an intermediate position since the sequence switch moved out of its first position, is moved to its lower position in which it completes connection with conductor 58 which extends through a conductor similar to 13 and through another In the fifth position of sequence switch 100, contacts 110 and 111 are closed, extending the line conductors to the cord finder switch B of Fig. 2.

The next step of the line finder sequence switch 100 is dependent upon an impulse which will be received over conductor 60 from sequence switch 200 of Fig. 2, through sequence switch contacts 112-5. It is therefore now advisable to trace the operation of the cord finder switch B up to the point at which it gives the impulse over conductor 60 for moving the sequence switch 100 out of its fifth position.

As previously described, sequence switch contact 106-34, Fig. 1, completes a circuit over conductor 41 through the operating magnet of sequence switch 200, Fig. 2, to battery and ground. The actuation of this magnet causes sequence switch 200 to move to its fourth position. In this position a circuit is completed from battery, through the coil of signal relay 69, sequence switch contact 302-1 of Fig. 3, sequence switch contact 205-4 of Fig. 2, and resistance to ground. This actuates relay 69, thereby lighting operators signal lamp 71 and closing the circuit from ground through contact 70, sequence switch contact 307-1, operating magnet of sequence switch 300, to battery, thus advancing this switch to its second position.

In the fourth position of sequence switch 200, contacts 206 and 207 are closed, thus connecting the calling subscribers line directly with one winding of the operators repeating coil 76, the middle terminals of this winding being connected to the opposite poles of a battery to furnish current for the calling subscribers transmitter. through sequence switch contacts 303-2 and 304-2. ,1

. sequence switch contacts 305-2 and 306-2, 4.;

even before an idle connecting cord .circuit at the operators position has been selected, thus enabling the operator to obtain the number of the desired line while the automatic selection of the connecting circuit is proceeding. I I

When sequence switch 200 reaches its fourth position, sequence switch contact 208 is closed and a circuit is completed for the brush clutch magnet 77 from battery, through'the coil of said magnet, sequence switch contact 208-4, and contact of test relay 63 to ground. This causes the rota-- tion of the brush carrying shaft 7 8 in a clockwise direction. As the brushes 79, 80, 81 and 82 wipe over the contact points on which various cord circuits terminate, the circuit through test relay 63 is brought into connection with the various test contacts of the cord circuits until an idle cord is reached. As will be hereinafter explained, the test contact points 83 of all idle connecting circults will have battery potential thereon. A c1rcu1t Wlll, therefore, be completed fro'm said contact point 83, through test brush 81,

sequence switch contact 203-4, one coil of relay Y64 and the winding of test relay 63 to ground thus actuating test relay 63. The

actuation of relay 63 opens its contact 62,

completes a clrcuit through sequence switch contact 2044'and through the winding of sequence switch operating magnet 200 to move the sequence switch out of its fourth and into its fifth position. In this position of the sequence switch, contacts 210-5 and 211-5 are closed, completing the circuit of the calling line through brushes 79 and 80 to it' he talking strands of the connecting cir- Clll Upon the arrival of test br-ush 81 upon sta tionary contact point 83, a circuit is completed from battery through sequence switch contact 402-1, and the coil of relay 85, contact point 83, brush 81, sequence switch contact 203-4, relays 64 and 63, to ground. Current through this circuit causes relay 85 to actuate, completing a circuit through its contact 86, sequence switch contact 403-1, and the coil of sequence switch operating magnet 400 to battery. This causes sequence switch 400 to move to its second position in which contacts 402 and 403 are opened 400, contact 406-2 is closed, completing the circuit of the connecting circuit indicating lamp 87, which indicates to the operator which of the particular connecting circuits at her position has been selected. The closing of sequence switch contacts 408-2, re ferred to in the preceding paragraph, completes a circuit from ground through relay 85, contact point 83 and brush 82, sequence switch contact 212-5, and the coil of the cord holding relay 90, to battery. Current in the path just described actuates relay 90, closing its contact 91 to complete a circuit through sequence switch contact 213-5, and the coil of sequence switch operating magnet 200 to battery, thus moving the sequence switch 200 out of its fifth and into its sixth position. In moving out of the fifth position, contacts 206 and 207 are interrupted, breaking the circuit first completed between the calling line and the operators telephone. In this posltion of sequence switch 200, contact 2145 is closed, thus completing circuit through conductor 60, sequence switch contact 112-5, and the coil of sequence switch operating magnet 100 to battery. This causes the sequence switch 100 to move out of its fifth and into its sixth position. When sequence switch 100 leaves its fifth position, contact 109 is opened and contact 114 is closed, thus shifting the control of the cut-off relay 9 from the line finder switch to the operators connector circuit, this circuit being now maintained through brush 81, contact 83, the coil of relay 85 and sequence switch contact 408-2 to ground. Position 6 of sequence switch 100 being the talking position, this switch is not again actuated until the release is desired.

Each of the sequence switches 100, 200 and 300 is now i'n its talking position, and the conversational circuit of the calling line is extended through to the connecting cord circuit and the operators telephone set. In a system of this sort, where any subscribers line may be extended to the operator over any cord circuit, the identity of the calling line is not disclosed. But in attending to a call, it is frequently necessary for the operator to know the number of the calling line in order that she may know the sort of service to which the line is entitled, that she may enter the charge against the particular line that is calling, if the line be a message rate line, or for other reasons. To furnish such identification of the calling line, there is associated with each of the lines, in the embodiment of the invention here illustrated, an impulse producing device or means for impressing upon each linea characteristic electrical condition; and the operator is provided with an indicating device that is responsive to the impulses or characteristic electrical condition impressed on the line, these devices being made operative to identify the line at the will of the operator.

In the embodiment of the invention illus trated, each line has associated with it a disk 14 having upon its periphery sets of teeth 15, which teeth are adapted in the rotation of the disk to act upon a switch 16 to cause its operation. The disk may be driven by means of a constantly rotating shaft with which it is coupled by means of a clutch magnet 17, the arrangement, with respect to the control of the movement of the disk, being similar to that of a sequence switch. The teeth 15 upon the disk 14 correspond with the digits in the number of the particular line with which the disk is associated. In the particular disk illustrated there are three teeth in the first group and five in the second, the associated line thus being identified as number 35. If the line number had a greater number ofdigits, there would be a greater number of groups of teeth on the identifying disk.

The switch 16 is so arranged that when a of identifying conductor 19 being controlled by a switch 93 adapted to be manipulated by the operator.' As is well known, this type of telegraph register has an electromagnet wh'ich operates, when the circuit through the register is closed, to release the tape feeding mechanism and make a mark upon the ta e.

Assuming that after conversing with t e calling subscriber the operator wishes to ascertain or check the number of the calling line, she closes the switch 93. -This causes the energization of the magnet of the telegraph register 61 and also that of the clutch magnet 17 of the impulse producing mechanism, this circuit being as follows: battery,

clutch magnet17, normally closed contacts of switch 16, contacts 53 of line relay 7, contact 42 and 'brush 4,0 of the line finder switch A, sequence switch contacts 1136, brush 82 and contact 89 of cord finder switch B, contacts of operators key 93, and telegraph register 61 to ground. The energization of clutch magnet 17 causes the disk 14 to rotate, and the energization of the magnet of register 61 makes a mark upon the tape. As the disk 14 rotates, it interrupts the circuit through the register 61 (in the case of this particular line) three times, then five times, for each revolution of the disk. This causes the mark upon the tape of the register 61 to be interrupted in a corresponding manner, thus recording the number of the calling line. This record continues to be received as long as the operator holds the key 93 closed, and is repeated at any time the operator wishes during the continuance of the connection by again closing the key. The circuit that is closed for the clutch magnet 17 through the resistance 18 provides for the continued rotation of the disk 14 during the intervals when the switch 16 is operating to produce the impulses in the circuit of the identifying conductor 19.

, sociated with the extension circuit of the line are controlled in sequence switch contacts 104 and 113. The conductor 19, to-

getherwith its branch closed in contacts 54 of the line relay 7 and itsbranch closed in contacts 104.4 of the sequence switch are 1 first employed in connection with the automatic identification of the calling line, which causes the brushes of the finder switch A to stop upon the terminals of that line; while the conductor 19 with its branch closed In contacts 53 of the line relay and its branch closed in sequence switch contacts 113-6 are laterv employed in connection with that identification of the calling line by means of which the operator is informed of the number of the calling line.

After the operator has terminated her conversation with the calling subscriber and has taken the first step toward securing connectionwith the desiredfsubscri bers line,

which may be either by means of automatic switches or a plug and jack, she depresses herlistening cut-off key 95, which closes a circuit through sequence switch contact 4092, and through the coil of sequence switch operating magnet 400 to battery. This causes sequence switch 400 to move out of its second and into its third Position. In this position, contacts 404 and 405 are opened, thus disconnecting the operators talking and listening set from the connecting circuit. The circuit through operators listening sequence switch 300 is at this time closed through sequence switch contact 412-25} and the switch returned to normal.

It is not 'deemed necessary to illustrate in detail the means for establishing an automatic connection or a manual connection with a desired line. It is to be understood, however, that when such a connection is established, the coil of supervisory relay 96 is serially included in the calling telephone line and thecoil of supervisory relay 97 is serially included in the called telephone line, current being fed to the transmitters of the respective .substationsfrom the central source of current through these coils.

At the termination of a conversation, the subscribers replace their receivers upon their switch hooks, and thus allow relays 96 and 97 to return to their normal-positions, and complete the circuits of the disconnect supervisory lamps, in the usual way, through sequence switch contact 4103. When the operator observes the display of both the calling and answering disconnect lamps, she depresses her clearing-out key 98, which completes a circuit through. se-

quence switch contact 411-3, and through the coil of sequence switch operating magnet 400.to battery and ground. This causes sequence switch 400 to move out of its third and into its first or normal position. As this occurs, sequence switch contact 410 is interrupted, .thus extinguishing the disconnect lamps. Contact 408 is now interrupted and the holding circuit of release relay 90 thereby opened, allowing its armature to return to its'normal position, closing contact 99 and completing a circuit from ground through contact 99, sequence switch contact 215 -6, and the coil of operating magnet 200 to battery and ground. Current in this path actuates the sequence switch 200, causing it to move out of its sixth and into its seventh positions. Between the sixth and the seventh position of sequence switch 200, contact 216 is momentarily closed, sending an impulse of current through contact 112-6, and the coil of sequence switch operating magnet 100 to battery and ground. Current in this path causes the sequence switch 100 to move out of its sixth and into its seventh position.

In the seventh-position of sequence switch 200, a circuit is closed for brush shaft operating magnet 77 from battery, throughsequence switch contact 2087, and contact 62 of relay 63 to ground. .This causes the brush shaft to rotate until track brush 250 comes in contact with plate 251, when a .circuit is completed from battery through resistance 2.52, track 251, track brush 250, contact arm 253, sequence switch contact 21-7-7 and relay 63to ground. This causes relay 63 to operate opening the circuit of magnet 77 at contact 62 and closing a circuit for holding magnet 84 by way of sequence switch contact 209-7 and contact 75 of relay 63. The closure of contact 75 also completes a circuit from ground through se-' quence switch contact 2047, and sequence of relay 29 to ground. Current in this path actuates magnet 43, causing the brush carrying shaft 44 to rotate again in a counter-clockwise direction. The rotation of this shaft will continue until'the track brush 37 engages the plate 39, at which time a circuit is completed from battery through theresistance 73, plate-39, brush 37, contact arm 38, sequence switch contact 103-7, and the coil of relay 29 to earth. Current in this path interrupts the circuit of clutch magnet 43 at contact 34, and closes the circuit for holding magnet 57 through contact 35 of relay 29 and the sequence switch contact 1087. The actuation of relay 29 also completes a circuit through contact 35, sequence switch contact 105-7, and the coil of sequence switch operating magnet 100 to battery. This causes the sequence switch to step to its eighth position, in which contact 103 is interrupted, permitting relay'29 to return to normal, and in which contact 107 is interrupted to prevent the brush carrying shaft 44 from being carried beyond its normal position. Contacts 105 and 108 are also opened at this time, the separation of contact 108 releasing the holding magnet, which now has no purpose. If sequence switch 200 has by this time returned to its normal position, a circuit is now completed through contact 2161, contact 112-8, and the coil of sequence switch operating magnet 100 to battery. Current in this path actuates the sequence switch 100, causing it to move out of its eighth and into its first or normal position, at the same time opening its contact 112. As sequence switch 100 returns to its normal position, contact 1021 is closed so that another call may be received by this line finder switch.

While this invention is shown and described with reference to a -particular embodiment, obviously it is susceptible of many modifications without departing from its spirit or scope.

What is claimed is:

- 1. In a telephone system, the combination with a plurality of telephone lines, a plurality of operators positions and means for extending any one of said lines to any one of said operators positions, of means associated with each of said lines for producing characteristic signal impulses, a signal receiving device at said operators position, means under the control of the operator for bringing said receiving device into association with the extended line to render the same responsive to said signal impulses to receive said signal, and means for repeating the transmission of said signal whenever said last mentioned means is operated.

2. In a telephone system, the combination with a plurality of telephone lines extending from their respective stations to a central oflice, of means associated with each line at the central ofiiee for producing impulses characteristic of said line, a plurality of operators positions, means for extending any one of said lines to any one of said operators positions, a signal receiving device at said operators positions, means under the control of the operator for bringing said signal receiving device into association with an extended line to receive said signal, and means for repeating the transmission of said signal whenever said last mentioned means is operated.

3. In a telephone system, the-combination signal whenever said last mentioned means is operated.

4. In a telephone system, the combination with a plurality of operators positions, of a plurality of lines of differing characteristics adapted to 'be extended thereto, means associated with each line for identifying the same with respect to its special characteristics, an indicating device at each of said operators positions responsive to said identifying means, means under the control of any one of said operators for bringing the said associated indicating device into association with any extended line, whereby a characteristic signal is received by said indicating device, and means for repeating the transmission of said signal whenever said last mentioned means is operated.

5. In a telephone system, the combination with a plurality of terminating lines diil'ering in their characteristics, normally inactive line-characterized identifying means associated with each line, a'plurality of line characteristic indicating devices responsive to said identifying means, operator-controlled means for bringing one of said indicating devices into temporary association with any of said lines and rendering active the identifying means associated with said line, whereby a characteristic signal is received by said indicating device,aand means for repeating the transmission of said signal whenever said last mentioned means is operated.

. 6. In a telephone system, the combination with a plurality of lines extending to a central ofiice, of a plurality of operators positions, means for extending any one of said lines to any one of said operators positions, an impulse producing device associated with each of said lines, the impulse devices assd ciated with the various lines differing from each other with respect to the character of the impulses produced, driving mechanism for each impulse device, an indicating device at each of said operators positions responsive to impulses, means under the control of an operator for bringing said indicating device into operative association with an extended line and simultaneously rendering active said driving mechanism, whereby a characteristic signal is received by said indicating device, and means for repeating the transmission of said signal whenever said last mentioned means is operated.

7. In a telephone system, the combination with a plurality of lines extending to a central office, of a plurality of extension circuits adapted to be brought into connection with any one of said lines, means at the central oflice for impressing upon each of said lines groups of impulses corresponding with the digits in the number of said line, an indicating device associated with each of said extension circuits, said indicating device being adapted to give indications correspond ing with the groups of impulses impressed upon the extended line, operator controlled means for bringing said indicating device into association with said extended line to respond to the impulses impressed thereon, whereby a characteristic signal is received by said indicating device, and means for re peating the transmission of said signal whenever said last mentioned means is operated.

8. In a telephone system, the combination with a plurality of lines extending to a central office, of a plurality of operators positions, means for extending any one of said lines to one of said operators positions, a normally inactive impulse producing device associated with each of said lines, said impulse device being adapted when operated to impress upon the associated line impulses characteristic of said line, an indicating device at each of said operators positions responsive to said impulses, means under the control of each operator for bringing said indicating device into association with an extended line and rendering the. associated impulse producing device active, whereby a characteristic signal is received by said indicating device, and means for repeating the transmission of said signal whenever said last mentioned means is operated.

9. In a telephone system, the combination with a plurality of lines extending to a central ofiice, each of said lines including a local conductor at a central office, of an impulse producing device included in the c rcuit of said local conductor, a plurality of operators positions, means for extending the circuit of anyone of said lines and its local conductor to any one of said operators positions, an indicating device in the extended circuit of said local conductor at said operators position, mears under the control of an operator for energizing said local conductor to render operative the impulse producing and indicating devices included therein, whereby a characteristic signal is received by said indicating device, and means for repeating the transmission of said signal whenever said last mentioned means is operated. a

10. In a telephone system, the combination with a plurality of lines extending to a centralofiice, each of said lines including a local conductor at the central office, an impulse producing device associated with each line at the central ofiice, said device comprising a circuit controlling part and a controlling magnet, an operators position, means for extending any one of said lines with its local conductor to said operators position, an indicating device at the operators position, a source of current, a switch under the control of the operator for including said source of current in said local conductor to energize said controlling magnet and render operative said impulse producing and said indicating devices, whereby a characteristic signal is received by said indicating device, and means for repeating the transmission of said signal whenever said last mentioned means is operated.

11. In a telephone system, the combination with a plurality of lines extending to a central office, of a normally inactive impulse producing device associated with each of a said lines at the central office, a plurality of operators positions, means for extending any one of said lines to any one of said positions, an indicating device at each position adapted for association with an extended line, operator controlled means for rendering said impulse producing device active, whereby a characteristic signal is received by said indicating device, and means for repeating the transmission of said signal wheanever said last mentioned means is operate 12. In a telephone system, the combination with a plurality of lines extending to a central oflice, each of said lines having a local identifying conductor at the central office, said conductor including means made operative when the associated line calls for identifying the line as a calling line and means for identifying the associated line with respect to its special characteristics, an extension circuit, a selector switch adapted to connect said circuit with any one of said lines, means controlling the movement of said selector switch, said means being adapted in the movement of said switch to be brought into operative relation with said identifying conductor and to be responsive to said calling line identifyin means, an indicating device associated with said extension circuit, and means for bringing said indicating device into operative relation with said identifying conductor to respond to said means for identifying the extended line with respect to its special characteristics.

In witness whereof we hereunto subscribe our names this 21st day of July, A. D. 1915.

EDWARD B. CRAFT. JOHN N. REYNOLDS. 

